Field of the Invention
Exemplary embodiments of the present invention relate to a vehicle exhaust heat recovery system; and, particularly, to a vehicle exhaust heat recovery system and method, capable of actively controlling an amount of coolant circulated through an exhaust heat exchanger, an engine, a radiator, and a water-cooled intercooler according to a temperature condition of the coolant, so as to improve fuel efficiency in a cold state.
Description of Related Art
Regulations of CO2 emission and fuel efficiency are increasingly reinforced by global warming all over the world. Fuel efficiency of a vehicle has been improved by improving combustion and power transfer processes until now. However, a study on improvement of fuel efficiency using heat lost by exhaust gas is actively ongoing in recent years.
An internal combustion engine of a vehicle uses thermal efficiency less than 40% from among 100% of heat energy of fuel used in the vehicle, and 30% of the heat energy is discharged as exhaust gas to the atmosphere and is discarded.
An exhaust heat recovery system is a system capable of shortening a preheating time of an engine to achieve improvement of fuel efficiency and reduction of exhaust gas, by heating coolant during initial starting of a vehicle using high-temperature exhaust heat discarded as described above.
However, the conventional exhaust heat recovery system requires complicated bypass devices, for example, so as to control a supply amount of exhaust gas flowing to the exhaust heat recovery system by installing a variable valve or the like at an end of an exhaust pipe and bypassing the exhaust gas according to opening and closing of the variable valve in order to control a degree of recovery of exhaust heat, as in Patent Document 1. For this reason, there is a problem in that the system has an increased capacity and mounting thereof is deteriorated.